Navigation Links
Zeroing in on the elusive green LED
Date:4/25/2011

Troy, N.Y. Researchers at Rensselaer Polytechnic Institute have developed a new method for manufacturing green-colored LEDs with greatly enhanced light output.

The research team, led by Christian Wetzel, professor of physics and the Wellfleet Constellation Professor of Future Chips at Rensselaer, etched a nanoscale pattern at the interface between the LED's sapphire base and the layer of gallium nitride (GaN) that gives the LED its green color. Overall, the new technique results in green LEDs with significant enhancements in light extraction, internal efficiency, and light output.

The discovery brings Wetzel one step closer to his goal of developing a high-performance, low-cost green LED.

"Green LEDs are proving much more challenging to create than academia and industry ever imagined," Wetzel said. "Every computer monitor and television produces its picture by using red, blue, and green. We already have powerful, inexpensive red and blue LEDs. Once we develop a similar green LED, it should lead to a new generation of high-performance, energy-efficient display and illumination devices. This new research finding is an important step in the right direction."

Sapphire is among the least expensive and widely used substrate materials for manufacturing LEDs, so Wetzel's discovery could hold important implications for the rapidly growing, fast-changing LED industry. He said this new method should also be able to increase the light output of red and blue LEDs.

Results of the study, titled "Defect-reduced green GaInN/GaN light-emitting diode on nanopatterned sapphire," were published last week in the journal Applied Physics Letters, and are featured in today's issue of the Virtual Journal of Nanoscale Science & Technology, published by the American Institute of Physics and the American Physical Society. The paper may be viewed online at: http://dx.doi.org/10.1063/1.3579255

The research program is supported by the U.S. Department of Energy National Energy Technology Laboratory (NETL) Solid-State Lighting Contract of Directed Research, and the National Science Foundation (NSF) Smart Lighting Engineering Research Center (ERC), which is led by Rensselaer.

LED lighting only requires a fraction of the energy required by conventional light bulbs, and LEDs contain none of the toxic heavy metals used in the newer compact fluorescent light bulbs. In general, LEDs are very durable and long-lived.

First discovered in the 1920s, LEDs light-emitting diodes are semiconductors that convert electricity into light. When switched on, swarms of electrons pass through the semiconductor material and fall from an area with surplus electrons into an area with a shortage of electrons. As they fall, the electrons jump to a lower orbital and release small amounts of energy. This energy is realized as photons the most basic unit of light. Unlike conventional light bulbs, LEDs produce almost no heat.

The color of light produced by LEDs depends on the type of semiconductor material it contains. The first LEDs were red, and not long thereafter researchers tweaked their formula and developed some that produced orange light. Years later came blue LEDs, which are frequently used today as blue light sources in mobile phones, CD players, laptop computers, and other electronic devices.

The holy grail of solid-state lighting, however, is a true white LED, Wetzel said. The white LEDs commonly used in novelty lighting applications, such as key chains, auto headlights, and grocery freezers, are actually blue LEDs coated with yellow phosphorus which adds a step to the manufacturing process and also results in a faux-white illumination with a noticeable bluish tint.

The key to true white LEDs, Wetzel said, is all about green. High-performance red LEDs and blue LEDs exist. Pairing them with a comparable green LED should allow devices to produce every color visible to the human eye including true white, Wetzel said. Today's computer monitor and television produces its picture by using red, blue, and green. This means developing a high-performance green LED could therefore likely lead to a new generation of high-performance, energy-efficient display devices.

The problem, however, is that green LEDs are much more difficult to create than anyone anticipated. Wetzel and his research team and investigating how to "close the green gap," and develop green LEDs that are as powerful as their red or blue counterparts.


'/>"/>

Contact: Michael Mullaney
mullam@rpi.edu
518-276-6161
Rensselaer Polytechnic Institute
Source:Eurekalert  

Related biology technology :

1. Elusive hot electrons captured in ultra-thin solar cells
2. Prototype NIST method detects and measures elusive hazards
3. Researchers measure elusive repulsive force from quantum fluctuations
4. Van Andel Institute Earns Highest "Green Building" Award
5. Plasma nanoscience needed for green energy revolution
6. China Green Material Technologies, Inc. Reports 2010 Financial Results
7. Smarter memory device holds key to greener gadgets
8. John W. Manzetti and the Pittsburgh Life Sciences Greenhouse Recognized as 2011 Outstanding Leader in Technology
9. Pittsburgh Life Sciences Greenhouse Announces the First Close of the PLSG Accelerator Fund LLC at $5 Million
10. The Pittsburgh Life Sciences Greenhouse Announces New Chairman of the Board
11. Syngenta and DuPont Announce Ownership Change at GreenLeaf Genetics
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Zeroing in on the elusive green LED
(Date:6/27/2016)... 27, 2016  Liquid Biotech USA ... of a Sponsored Research Agreement with The University ... (CTCs) from cancer patients.  The funding will be ... correlate with clinical outcomes in cancer patients undergoing ... then be employed to support the design of ...
(Date:6/24/2016)... (PRWEB) , ... June 24, 2016 , ... While the ... such as the Cary 5000 and the 6000i models are higher end machines that ... the height of the spectrophotometer’s light beam from the bottom of the cuvette holder. ...
(Date:6/23/2016)... , June 23, 2016   Boston Biomedical ... novel compounds designed to target cancer stemness pathways, ... been granted Orphan Drug Designation from the U.S. ... of gastric cancer, including gastroesophageal junction (GEJ) cancer. ... designed to inhibit cancer stemness pathways by targeting ...
(Date:6/23/2016)... ... June 23, 2016 , ... ... and Mold) microbial test has received AOAC Research Institute approval 061601. , “This ... introduced last year,” stated Bob Salter, Vice President of Regulatory and Industrial Affairs. ...
Breaking Biology Technology:
(Date:4/14/2016)... 14, 2016 BioCatch ™, ... today announced the appointment of Eyal Goldwerger ... Goldwerger,s leadership appointment comes at a time ... the deployment of its platform at several of the ... which discerns unique cognitive and physiological factors, is a ...
(Date:3/31/2016)... 2016  Genomics firm Nabsys has completed a financial ... Bready , M.D., who returned to the company in ... leadership team, including Chief Technology Officer, John Oliver ... Nurnberg and Vice President of Software and Informatics, ... Dr. Bready served as CEO of Nabsys from ...
(Date:3/22/2016)... 2016 According to ... for Consumer Industry by Type (Image, Motion, Pressure, ... & IT, Entertainment, Home Appliances, & Wearable ... 2022", published by MarketsandMarkets, the market for ... USD 26.76 Billion by 2022, at a ...
Breaking Biology News(10 mins):